The present invention relates to seals placed between two structural members to provide resistance to fire propagation, and in particular to such seals using a preformed strip of fire resistant material.
In building construction, particularly concrete wall construction, gaps often exist between adjacent structural members. Such gaps can result from the use of prefabricated structural elements, or may be formed in place to allow for expansion of the structural elements. In either event, acceptable fire resistance requires that the gaps be sealed so that fire cannot readily propagate through the gaps between structural members.
The conventional technique for sealing gaps between structural members for fire resistance is to fill the gap with poured in place silicone foam material. Initially, a dam is formed in one end of the gap to provide an enclosed cavity. Next, silicone foam material is poured into the cavity, and allowed to set. Once the silicone foam is set, the dam is removed. This technique provides an acceptable seal unless poor workmanship is employed, which can result in voids in the sealing material which significantly degrade its resistance to fire propagation. This technique is relatively expensive in that it involves a large amount of hand labor.
Attempts have been made to provide a fire resistant seal by inserting a preformed strip of fire resistant material, as illustrated in British Pat. No. 1,434,649. However, the device proposed by the British patent is relatively complex, requiring refractory material adhering to a metallic spring, with silicone foam material embedded in the spring. Such devices are relatively impractical and are not commonly used.
The concept of inserting a preformed plastic strip into a gap between two structural materials for purposes other than fire resistance is not new. For example, such devices are shown in U.S. Pat. Nos. 3,286,425; 3,923,401; 4,023,324; and French Pat. No. 1,283,939. However, these devices leave air spaces within the seal, which is unacceptable for fire resistance. The only exception in U.S. Pat. No. 4,023,324, which requires that material be poured in place.